1. Field of the Invention
This application relates to a lens array unit for use in an information processing apparatus such as an image forming apparatus or an image reader, and also relates to an optical head that includes the lens array unit. Additionally, the application relates to the information processing apparatus that includes the optical head.
2. Description of the Related Art
A rod lens array unit is well known as a conventional lens array unit. The rod lens array unit may be used in an electrophotographic image forming apparatus with an LED (Light-Emitting Diode) head in which LEDs are linearly arranged or in an image reader such as a scanner or a facsimile machine that reads an image on a document by using a light receiving unit in which light receiving elements are linearly arranged. An optical system including the rod lens array unit can form an erected equal magnification image of an object.
Another conventional lens array unit includes two lens array plates that are arranged parallel to form an erected equal magnification image of an object. Micro lenses are linearly arranged on each of the lens array plates. The lens array plate with the micro lenses can be made by plastic injection molding. Japanese Patent Laid-Open No. 2000-221445 discloses one such lens array unit.
In the aforementioned lens array unit, however, if the lens array plate on which the micro lenses are linearly arranged is made by plastic injection molding, the micro lenses are not uniform in shape. This is due to temperature non-uniformity of a mold in a longitudinal direction of the lens array plate, and the difference in resin injection pressure between that in the vicinity of a gate, or a resin inlet of the mold, and that at a location distant from the gate. Therefore, the conventional lens array unit is unable to form an image of an object at a desired resolution.